There is an almost uniform occurrence of peripheral neuropathy in patients with longstanding diabetes mellitus. Recently, we found that there is thickening of the basement membranes of the perineurial cell, Schwann cell, and capillary endothelial cell in diabetic peripheral nerves. These basement membrane changes and the accompanying peripheral neuropathy have not been studied in a correlative prospective manner in terms of their clinical, structural, and biochemical features. The overall aim of the proposed project is to perform such a study. Samples of peripheral nerve from multiple sites and skeletal muscle will be obtained from diabetic and nondiabetic patients coming to autopsy. Quantitative morphologic study of the nerves and muscle will evaluate basement membrane changes and diease states (i.e., peripheral neuropathy). Basement membrane will be isolated from these nerves by a newly devised method and will be analyzed biochemically. Patient data will be collected (i.e., duration of diabetes, type of therapy, age, etc.) for correlation with the anatomical and biochemical data.